The invention relates to an improved fire resistant air transfer grille or damper, used particularly, but not exclusively, as ventilation means in fire and smoke resistant doors, walls and ventilation ducts.
Large buildings, especially industrial buildings, are often split into a number of self-contained areas by fire and smoke resistant walls and doors. It is often necessary to ventilate these areas, and hence a number of air transfer grilles or dampers are required to allow the through flow of air into and out of the self-contained areas.
However, in the event of a fire, these air transfer grilles or dampers also allow the through flow of smoke, hot gases and in extreme situations, flames.
It is thus desirable to use an air transfer grille or damper that does not allow the through flow of smoke, hot gases and flames in the event of a fire. Such an effective air transfer grille is one that incorporates a plurality of slats, wherein each of the slats has an intumescent core.
When used in fire and smoke resistant walls and doors defining a room or other distinct area, air transfer grilles or dampers incorporating intumescent slats allow the through flow of air in and out of the room.
In the event of a fire, high temperatures cause the intumescent slats to swell to many times their original thickness, fusing together to form a non-combustible mass which provides fire resistance to match the surrounding construction and prevent the through flow of hot gases, smoke and flames.
The intumescent slats may be provided with elongate reinforcing channels as protection along their edges. Hitherto the channels have been welded into position within an outer frame by spot welds, as shown in FIGS. 5-8. The use of spot welds in the manufacture of such grilles or dampers, however, is expensive due to the number of spot welds required, and the jigs required for each different size grille.
According to an aspect of the invention, there is provided a fire resistant air transfer grille or damper comprising:
a frame defining a gas transfer path, the frame including two opposed wall portions, each including at least one recess;
a slat including a core of intumescent material and having at least one elongate edge whereby the or a said edge is receivable at either end of the slat in a pair of the recesses respectively in the opposed wall portions; and
a retainer for retaining the slat in the said recesses whereby the slat permits gas flow along the gas transfer path when unswollen and closes the gas transfer path on tumefaction.
An advantage of the invention is that spot welds are not required to secure the slat into position, as the slat is retained in position within recesses in the opposed wall portions of the frame by a retainer. This provides a much simpler method of assembly, and also provides a more robust product in use, as the risk of weld failure is removed.
In a preferred embodiment of the invention the retainer is a mirror image of the frame and so includes two opposed wall portions that each include at least one recess. In this preferred embodiment, the slat has a second elongate edge that is receivable at either end of the slat in a pair of the recesses respectively in the opposed wall portions of the retainer.
The frame and the retainer may be secured together by securing means, and are preferably secured together by a number of sleeve-bolts inserted through apertures in the retainer and the frame.
The use of sleeve-bolts prevents deformation of the frame components when the bolts are tightened.
An elongate channel member may be provided on the or each of the elongate edges of the slat. These elongate channel members protect the elongate edges of the slat that are receivable in recesses in the frame and, when required, in the retainer.
Preferably the elongate channel members are made from steel.
In a further embodiment of the invention, a plurality of slats each including a core of intumescent material and having at least one elongate edge are included within the fire resistant air transfer grille or damper. In this embodiment of the invention, the opposed walls of the frame each include a plurality of recesses and the or a said elongate edge of each of the plurality of slats is receivable at either end of the slat in a pair of recesses respectively on the opposed wall portions. The retainer retains the slats in the recesses, and in a preferred embodiment, the retainer is a mirror image of the frame and the slats each include a second elongate edge. The second edge of each of the plurality of slats is then receivable at either end of the slat in a pair of recesses respectively on opposed wall portions of the retainer.
In embodiments of the invention where the fire resistant air transfer grille or damper includes a plurality of slats, the or an elongate edge of each of the slats may be received at either end of the slat in a pair of recesses respectively so that the slats are arranged parallel to each other.
The frame and retainer may be rectangular in shape so producing a rectangular fire resistant air transfer grille or damper. The slat or slats may also be rectangular, each slat then having two elongate edges extending parallel to each other.
The slats may be made from PVC or metal with an intumescent material provided within the slat to provide an intumescent core.
Preferably the slats are made from aluminium with an intumescent material provided within the aluminium slat to provide an intumescent core.
The aluminium acts as a protective layer and gives a quick sealing response and added resistance to erosion of the intumescent material when subjected to high velocity hot gases.
In preferred embodiments, the outer frame is made from steel. Such an outer frame contributes to fire performance by preventing inward deformation of surrounding structures and protecting the intumescent material within the grille or damper.
The use of a fire resistant air transfer grille or damper according to a preferred embodiment of the invention has been found to provide fire resistance of up to four hours, and consistently achieve a complete seal in two minutes, when tested in accordance with BS 476 Parts 20 and 22, and similarly internationally recognised standard methods of test. In some circumstances a complete seal is achieved in as little as ninety seconds.
An embodiment of the invention has also been found to be resistant to the onerous impact, erosion and cooling effects of the xe2x80x9cHose Streamxe2x80x9d test applied after exposure to typical American fire test regimes such as UL 10C.
According to a further aspect of the invention there is provided a method of manufacturing a fire resistant air transfer grille or damper including the steps of:
positioning a slat including a core of intumescent material and having at least one elongate edge, so that the or a said edge is received at either end of the slat in a pair of recesses respectively in opposed wall portions of a frame; and
positioning a retainer so that it retains the slat in the said recesses.